1. Field of the Invention
This invention relates to a method and apparatus for attaching fitment tubes to flexible films suitable for the packaging of medical solutions. In particular, the present invention relates to a method and apparatus for attaching fitment tubes to flexible films in the form of pouches which retain their clarity after filling and heat sterilization of medical solutions contained therein.
2. Description of the Related Art
Currently, it is common medical practice to supply liquids such as medical solutions for parenteral administration in disposable, flexible pouches. These pouches should be characterized by collapsibility, transparency, and adequate mechanical strength. They must also be able to resist the relatively high temperatures required for heat sterilization of their contents, for example in an autoclave. Typically, medical solutions and the like are autoclaved at about 253.degree. F., for periods of 15 to 30 minutes.
Commonly, such flexible pouches are typically made from a highly plasticized polyvinyl chloride. While meeting the requirements mentioned above, polyvinyl chloride may have some undesirable properties for use as a medical solution pouch because of the possibility of migration of plasticizer from the polyvinyl chloride into the medical solution or the other contents of the pouch so that the solution may become contaminated by potentially toxic material. A question has also arisen concerning whether PVC is adequately chemically neutral to medical solutions. It has also been found that polyvinyl chloride becomes brittle at relatively low temperatures.
In these flexible pouches it is desirable to include means for accessing the container (hereinafter "fitments"). Fitments provide a means for establishing fluid communication between the container and the outside environment.
Flexible pouches with fitments can be produced by form, fill and seal packaging machines. Form, fill and seal packaging machines provide an apparatus for forming a web of film into a flexible container housing a desired product. Typically, these machines include a former or mandrel, a fill tube, and heat sealers. The former or mandrel forms or folds the web of film into a tubular shape around a fill or film tube. The film tube is utilized to dispense the material to be packaged into the tubular shaped web of film. In these typical form, fill and seal packaging machines, fitments are attached with an impulse heat sealing system. Typical apparatus of this type is disclosed, for example, in U.S. Pat. No. 4,779,397 issued to Christine et al. Another form of this type of apparatus is disclosed in U.S. Pat. No. 4,695,337 issued to Christine. A vertical form, fill and seal apparatus for making three side fin pouches is disclosed in U.S. Pat. No. 4,947,621 issued to Christine et al.
Fitments suitable for sealing directly to a film web in apparatus as described hereinabove are, for example, those disclosed in U.S. Pat. No. 4,445,550 issued to Davis et al and U.S. Pat. No. 5,110,041 issued to Keeler. These fitments are not adaptable for use on fitment tubes, but instead must be sealed directly to the pouch film web.
Flexible pouches suitable for medical solutions which do not have the drawbacks of PVC and which maintain their clarity as well as their collapsibility, and mechanical strength are known, for example, from U.S. Pat. No. 4,643,926 issued to Mueller and U.S. Pat. No. 4,891,253 issued to Mueller. Sealing fitment tubes to these films using impulse sealing and RF sealing do not produce the necessary seal integrity to prevent leaking, however.
Another method of sealing a fitment tube to a flexible pouch is disclosed in European Pat. No. EP-269419-A issued to Craig Med. Prod. Ltd., wherein a separate sleeve of material is placed over the fitment tube and crimped and then heat sealed. This sleeve is a critical part of the invention required to realize the seal between the fitment tube and the flexible pouch.
Traditionally these flexible pouches are made of PVC and the fitment tubes, also of PVC, are sealed to the pouches using RF energy. RF energy, however, does not produce the necessary hermetic seal with many of the flexible films which retain their clarity as well as their flexibility and strength. Likewise, impulse heat sealing has been utilized with PVC in the past, but it too fails to provide the necessary hermetic seals due to limitations of forming the heated wire in the shapes necessary to seal a circular cross section fitment tube to a pair of flat sheets of flexible film.
Thus, there is a need for a method and apparatus to attach fitments to flexible pouches which overcome the limitations of PVC flexible pouches and also produce and maintain a strong, leak free, hermetic seal between the fitments tubes and the flexible film web.